Women who gain or lose a lot of weight between pregnancies face an increased risk of premature birth, stillbirth, and high blood pressure.

Irish obstetricians Dr. Jennifer Walsh and Professor Deirdre Murphy made that surprising observation in an editorial in the British Medical Journal.

The doctors cited a Swedish study of over 200,000 women who were monitored from their first pregnancies to the beginning of their second pregnancies.

Even a small increase in a woman’s Body Mass Index (BMI) increased the risk of high blood pressure, diabetes and stillbirth.

In another study quoted by the obstetricians, a woman whose BMI fell by 5 units or more before her second pregnancy risked premature delivery. The risk was even higher for women with a previous premature birth.

This second study was published in the American Journal of Obstetrics and Gynecology last year.

Dr. Walsh and Professor Murphy recommend that women maintain a healthy and consistent weight before, during and after pregnancy to reduce these risks.